In this work, systematic studies were carried out on SLS (selective laser sintering) printed samples, with two different geometries, standard test samples dumb-bells (dog bones) and tubes (Ã 30 mm and 150 mm long), consisting of two different materials, viz. PA12 (polyamide) with and without the addition of carbon fibres (CFs). These samples were tested according to their respective ISO standards. The standard test samples exhibited relatively small differences with regards to printing directions when PA12 was used alone. Their tensile strengths (Ïm) were approx. 75%â80% of the injection-moulded sample. The addition of carbon fibres significantly enhanced the tensile strengths, namely 50% greater for the vertically printed test sample and more than 100% greater for the horizontally printed samples, compared to the respective objects consisting of PA12 alone. The strong difference in printing directions can be attributed to the orientation of the carbon fibres. Mechanical tests on the SLS printed tubes confirmed the trends that were found in the standard test samples. Porosity and pore structure inside the SLS printed tubes were studied by combining optical microscopy and X-ray microtomography with image analysis. It was found that porosity was a general phenomenon inside the SLS printed samples. Nevertheless, there were significant differences in porosity, which probably depended on the properties of the materials used, both with and without carbon fibres, thus causing significant differences in light absorption and heat conductivity. The printed samples made of PA12 alone possessed quite a high level of porosity (4.7%), of which the size of the biggest pore was hundreds of microns. The twenty biggest pores with an average size of 75*104 ÎŒ m3 accounted for 43% of the total porosity. However, the porosity of the printed samples made from PA12 + CF was only 0.68%, with the biggest pore being only tens of microns. The corresponding average pore size of the 20 biggest pores was 72*103 ÎŒ m3, which was one order of magnitude smaller than the printed samples made from PA12 alone. Pores inside the SLS printed samples were probably responsible for a spread in the mechanical properties measured, e.g. tensile strengths, tensile (Young’s) modulus, strain at break, etc. The ratios of their standard deviations to their corresponding mean values in the standard test samples could probably be used as an indicator of porosity, i.e. the bigger the ratio, the higher the porosity.

Additive manufacturing (3D printing) enables the designing and producing of complex geometries in a layer-by-layer approach. The layered structure leads to anisotropic behaviour in the material. To accommodate anisotropic behaviour, geometrical optimization is needed so that the 3D printed object meets the pre-set strength and quality requirements. In this article a material description for polymer powder bed fused also or selective laser sintered (SLS) PA12 (Nylon-12), which is a common 3D printing plastic, was investigated, using the Finite Element Method (FEM). The Material Model parameters were obtained by matching them to the test results of multipurpose test specimens (dumb-bells or dog bones) and the model was then used to simulate/predict the mechanical performance of the SLS printed lower-leg prosthesis components, pylon and support. For verification purposes, two FEM designs for a support were SLS printed together with additional test specimens in order to validate the used Material Model. The SLS printed prosthesis pieces were tested according to ISO 10328 Standard. The FEM simulations, together with the Material Model, was found to give good estimations for the location of a failure and its load. It was also noted that there were significant variations among individual SLS printed test specimens, which impacted on the material parameters and the FEM simulations. Hence, to enable reliable FEM simulations for the designing of 3D printed products, better control of the SLS process with regards to porosity, pore morphology and pore distribution is needed.

Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area production capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheology, printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temperature sensitive substrates that cannot withstand sintering of high temperature. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, electrical sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.

Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area production capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheology, printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temperature sensitive substrates that cannot withstand sintering of high temperature. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, electrical sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.

The temperature dependency and reversibility of the sheet resistance of silver nanoparticles covered by 3-mercaptopropionic acid (Ag-MPA) molecules, used in the printed temperature sensor, has been investigated. The microstructural evaluation, the FTIR spectra and thermal property analyses of the Ag-MPA films suggest co-existence of both weakly adsorbed as well as firmly adsorbed MPA molecules on the surface of Ag nanoparticles. The weakly adsorbed MPA molecules was to a great extent be desorbed and removed from the surfaces of silver nanoparticles when heated up to 180 °C for the first time. While the firmly adsorbed MPA molecules remain on the surfaces of silver nanoparticles even at higher temperature. Yet the firmly adsorbed MPA molecules are likely having gone through a transformation circle from/to the gauche and trans conformations in correspondence to a heating and cooling cycle, which results in temperature dependent and reversible sheet resistance. The MPA molecules in the gauche conformation are more densely packed on the surface of silver nanoparticles and can hinder the electron’s movability within the Ag-MPA film. While in the trans conformation with lower ‘surface space’ coverage by the MPA molecules, electrons move more freely within the film. Based on the temperature dependent nature, the fully printed temperature sensor using the Ag-MPA nanoparticles as the functional layer was made, of which the highest sensitivity is 5.12% °C−1 at 200 °C.

For the first time in the Bioeconomy research program at RISE, corrugatedboard has an own research area. Research is building around the main driving forcesin the corrugated board value chain like e-commerce, improved box performance anddigital printing. The main weakness of corrugated board, its moisture sensitivity, isalso addressed.These main driving forces and weaknesses of corrugated board are mirrored in thethemes of this large research program area:Fibre sorption and deformation mechanismsFundamental knowledge on the mechanisms behind moisture sorption and deformation on fibre level is developed to increase moisture and creep resistance throughmodification of paper materials. State of the art methods for characterization ofthe fibre ultra- and nano-structure such as Fourier transform infra-red spectroscopy(FTIR), small angle X-ray scattering (SAXS), and wide angle X-ray scattering (WAXS)give new insights on mechanisms and clarify effects of moisture as well as chemicalmodifications.Papermaking for improved base sheetsConcepts that are explored are fibre-based strength additives produced with novelrefining techniques, and modified ZD-profiles in the sheet for better mechanical properties.Box mechanicsMechanical performance of structures such as corrugated board boxes can be predicted through physically based mathematical modelling by taking the behaviour ofthe constituent materials as well as the geometry into account. Appropriate materialmodels for the corrugated board are identified and finite element models for simulation of corrugated board packaging performance are developed.Tool for inkjet printability on corrugatedThere is a genuine need for improved inkjet printability on corrugated materials thanksto rapid development in e-commerce as well as digitalization along the corrugatedvalue chain. Effective measurement methods and knowledge around ink-substrateinteractions are developed to enable board producers and converters to have effective product development and predictable printability on not only liners but also oncorrugated materials.

Many commercial materials (papers and boards) contain optical brightening agents also known as fluorescent whitening agents. Adequate adjustment of the UV content of a measurement device (e.g., spectrophotometers) is essential for accurate color measurement. As specified in the ISO standards, the UV content is adjusted against an assigned value of an international reference transfer standard, for example, CIE whiteness (D65/10Â°) for the CIE illuminant D65 or ISO brightness for the C illuminant. Because of the simplicity, these approaches have gained great popularity in papermaking industry. Yet, there has been little evidence indicating how accurate the total spectral radiance factor corresponding to the single assigned value is reproduced. Hence, we present a method that quantitatively evaluates the accuracy of the UV-adjustment technique, through comparing the total spectral radiance factors obtained from UV adjustment with the assigned ones. This method has been applied to three second-level international reference transfer standard illuminated by three standard illuminants, D65, C, and D50. We found that the major differences between the assigned spectra and those obtained from the UV adjustments occur in the blue band where fluorescence is strong. At a few wavelengths, the differences may be up to 4-5%. Nevertheless, their color differences corresponding to the assigned spectra and those obtained from the UV adjustments are still smaller than unity (1 ÎE*) for all of the illumination conditions. Two instruments using the representative UV adjusting techniques, for example, the conventional UV-adjusting with an adjustable (GG395) UV filter and the numerical UV-filtering, have been studied.

Spectral reflectance, radiance factors, gloss etc of paper and textile are often regarded as intrinsic properties of the materials alone. But in practice, instrumental readings of these properties depend even on the instruments setups, for instance, illumination/detection geometries, UV contents of the illumination, measurement areas etc. Comparative studies with four commercial spectrophotometers of three illumination/detection geometries, Diffuse/0-deg, Diffuse/8-deg and 45-deg/0-deg, have been conducted. These geometries are used in paper, textile and graphic industries, respectively. The materials analysed in this study include white and colour papers and textiles. The white papers contain fluorescent whitening agents (FWAs) whose excitation energies are only in UV wavelength bands. On the contrary, the colour papers have fluorescent agents whose excitation energies are in the visible wavelength bands, according to our measurements. Textile reference standards of different whiteness values are also included in order to study the influences from surface texture. The study confirms the strong influences of instruments setups, e.g. illumination/detection geometries, UV contents of the light sources etc, on the measured results. The study also reveals the significant influences from the combination of instrumental setups with the structural and surface characteristics of the measured samples.

Print through is an often encountered defect of printed maters, especially on paper grades of low and medium grammages. Print through phenomena have two contributing components, show through and strike through, resulting from insufficient paper opacity and ink penetration, respectively. The existing measurement method of print through and its components are calculated from a set of spectral reflectance values of printed and non-printed paper samples. These reflectance values are from rather big areas that equal to the opening of the employed spectrophotometer (say 33 mm in diameter). Thus, the calculated print through, show through and strike through, are only average values of the measured areas. This method has intrinsic weaknesses as paper is an inhomogeneous medium whose structure and materials compositions vary from one position to another, leading to inhomogeneous show through and strike through (opacity and ink penetration) across the measured areas, especially for papers of low and medium grammages.In this report we present a new method that enables one to take into account of variations in print through across the measured areas. The method employs a scanner that scans the printed and unprinted samples into RGB images of desired spatial resolutions. With the help of calibration patches that are simultaneously scanned as the measured samples, the RGB image signals can be converted into reflectance values. These reflectance values are then used to compute the print through, show through and strike through. Moreover, by means of Kubelka-Munk model, the depth of ink penetration at each spatial position can also be obtained. The developed method has been implemented in Matlab and successfully been applied to printed samples of newsprint and office papers. Comparative studies between instrumental measurements and perceptual evaluations confirm that the print through variations across the printed areas have strong influences on the print quality assessments. It is also found that using internal size agents in paper making is helpful for reducing ink-penetration.

An effective method is proposed that enables one to simultaneously analyze details of numerous holographic grating patterns over a large area. Unlike the conventional approaches relying on sophisticated lighting and optical systems and dark environment, only a flatbed scanner is needed. Thanks to the ârotate-scanâ measurement strategy, details of the holographic grating patterns can be obtained, e.g., spatial distribution of the grating patterns, interval and orientation of the grating grooves within each grating pattern, and defects of the holographic patterns. The method has been verified by applications to two holographic papers of different grating intervals and orientations. The measured values agree well with those obtained with a light optical microscope (LOM). The proposed method is applicable to both transparent and reflective holographic materials of broad grating periodicity.

A model of inkjet printing dynamics has been developed that enables a comprehensive view to be obtained of the relationships between the characteristics of the ink droplet (volume, striking speed, viscosity and surface tension), substrate properties and interactions between the ink and the substrate. Simulations based on the three equations that are the major results of the model have provided an understanding of the basics of inkjet printing. Pressure profiles resulting from ink-striking by ink droplets of different volumes and jetting speeds have been obtained. The time duration of the striking process was in the order of microsecond and the peaks of the striking pressure were solely dependent on the jetting velocities, while the duration time of the striking processes was dependent only on the droplets volumes. The penetration length (depth) was heavily dependent on the contact angle. For a coated surface of small pores, the initial penetration depth was 0.26 micron when the striking speed was 30m/s. For a larger pore, the corresponding depth was 1.30 micron.

A series of anthracene-based derivatives, namely, 9-(4-phenyl)anthracene(1), 9-(4-phenylethynyl)-anthracene(2) and 9, 10-bis(phenylethynyl)anthracene(3), was synthesized by the Suzuki/Sonogashira cross-coupling reactions in good yields. These compounds were fully characterized by X-ray crystallography, thermogravimetric analysis(TGA), differential scanning calorimetry(DSC), UV-Vis absorption and fluorescence(FL) spectroscopy, as well as density functional theory(DFT) calculations. Single-crystal X-ray analysis revealed that the packing structures were influenced by the terminal substitutions. All the compounds exhibited high thermal stability(Td=221â484 Â°C) and blue emission with a high quantum yield(ÎŠf =0.20â0.75). As the number of substituents increased, the decomposition temperatures(Td) of these compounds increased in the following order: 1&lt;2&lt;3. Experiments on the photophysical properties revealed that different substituents strongly affected the optical properties. In particular, compound 1b with the electron-withdrawing group(âCHO) exhibited a larger Stokes shift(113 nm) than the other compounds. Investigation of the electrochemical properties of these compounds showed that the HOMO-LUMO energy gaps(Egap) decreased obviously as the degree of conjugation increased.